Cellular phones have evolved from large devices that were only capable of analog voice communications to comparatively smaller devices that are capable of digital voice communications and digital data communications, such as Short Message Service (SMS) for text messaging, email, packet switching for access to the Internet, gaming, Bluetooth, and Multimedia Messaging Service (MMS) to provide some examples. In addition to these capabilities, the cellular phones of today have additional non-communication related capabilities, such as a camera with video recording, an MPEG-1 Audio Layer 3 (MP3) player, and software applications such as a calendar and a phone book, to provide some examples. Even in light of these capabilities, manufacturers of cellular phones are placing even more capabilities into cellular phones and making these more power cellular phones smaller.
At the heart of each cellular phone lies a power management unit (PMU). The PMU is responsible for monitoring power connections and battery charges, charging batteries when necessary, and controlling power to other integrated circuits, as well other power functions of the cellular phone. The PMU may include one or more voltage regulators, such as switching regulators or linear regulators to provide some examples, to control power to other integrated circuits of the cellular phone. One type of voltage regulator commonly used is a buck switching regulator. The most popular buck switching regulators for cellular phones, and wireless devices in general, are current programmed mode converter and the hysteresis control converter. The current programmed mode converter exhibits good load regulation and audio-susceptibility, however, its control bandwidth is not wide and its load-step performances are poorer than those of hysteresis control converters. On the other hand, hysteresis control converters have faster load-step response but poorer load regulation when compared to current programmed mode converter.
Thus, there is a need for a switching regulator that combines the advantages of the current programmed mode converter and the hysteresis control converter that overcomes the shortcomings described above. Further aspects and advantages of the present invention will become apparent from the detailed description that follows.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.